Benzofuran derivatives or pyridofuran derivatives of the formula [I]:
wherein X is a group of the formula: —N═ or —CH═; R1 is a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxy group, a cyano group or an amino group optionally substituted by a lower alkyl group; Ring A is a nitrogen-containing heterocyclic group; Ring B is an optionally substituted benzene ring or an optionally substituted pyridine ring; and R3 is a hydrogen atom or a lower alkyl group, or a pharmaceutically acceptable salt thereof, which is useful as a medicament, particularly as an inhibitor of activated blood coagulation factor X, and a process for preparing the same are disclosed in WO03/082847 and Japanese Patent Application No. 2003-84865 (JP-2004-250417, A).
However, the process disclosed in WO03/082847 and Japanese Patent Application No. 2003-84865 (JP-2004-250417, A) involves many steps, and, therefore, the development of an industrially advantageous manufacturing process involving fewer steps has been demanded.